This invention relates to high speed, high torque automatic machine tools, and more particularly, to apparatus for quickly and securely locking a tool holder/adapter to a drive spindle associated with the machine tool.
Modern high speed machine tools employ many different types of tools for drilling, boring, milling, etc., in its machining operation. Each tool is mounted to a tool holder/adapter which is selectively engaged by the machine's drive spindle to perform the desired machining operation. U.S. Pat. No. 3,999,769 discloses one such tool holder/adapter.
Desirably, the tool holder/adapter cooperates with the drive spindle to permit quick and secure changing from one tool to another. When not in use, the tool holder/adapter is stored in a turret on the machine. When a tool is to be used, the turret is moved to align the tool holder/adapter with the drive spindle, which is then moved downwardly to engage the tool holder/adapter and release it from the turret. U.S. Pat. No. 3,999,769 discloses a spindle which includes a step-shaped nose for engagement by the tool holder/adapter. The tool holder/adapter includes a straight-sided central recess for receiving the nose, an upwardly-biased peripheral retainer cup or locking ring, and a lock pin and a detent pin mechanism, all of which are intended to selectively secure the tool holder/adapter to either the spindle nose or the turret.
The locking mechanism includes three radially movable lock pins, each end of which is provided with a shaped face. Each locking pin is movable within a passageway toward and away from the central recess. An axially-movable spring-loaded detent pin is provided for cooperation with each locking pin. The detent pin is positioned partially in the passageway and partially in the central recess.
In the stored position in the turret: (1) the peripheral retainer cup is held in a downward position; (2) the lock pin is positioned radially outwardly with its inner end fully within the passageway and its outer end engaging the turret; and (3) the detent pin is positioned upwardly and contacts a portion of the inner face of the lock pin within the passageway and is intended to hold the lock pin in the outward position. When the drive spindle is moved into the central recess, it is intended that it engage the top side of the detent pin, and push it downwardly so as to release the lock pin and permit it to move inwardly into the recess. As the drive spindle urges the tool holder/adapter downwardly, the lock pin moves inwardly, the outer end releases from the turret and the inner end engages the stepped spindle nose. At the same time, the retainer cup moves upwardly to prevent the lock pin from moving outwardly and releasing the nose until the tool holder/adapter is returned to storage.
Although this system is intended to provide positive locking to the spindle and to the turret, it has been found: (1) that the tool holder/adapters have been driven from the turret without engaging the spindle nose; and (2) that positive locking to the turret for storage has not always been achieved.
The reason for the foregoing problems appears to be related to improper functioning of the locking pin due to sticking or slippage of the detent pin. For example, if only one of the detent pins sticks and fails to engage the associated locking pin, the tool holder/adapter may not lock securely to the turret. Thus, the locking pin may extend into the central cavity so that: (1) when the spindle nose enters the recess, it will strike the top of the locking pin, thereby driving the holder/adapter from the turret, without the nose being securely engaged; or (2) the tool holder/adapter may work loose from the turret during operation of the machine.
It is also possible that due to the sloped and mating surfaces of the detent pin and locking pin, the locking pin can work against the detent pin in a cam-like manner so as to urge the detent pin downwardly and (1) permit the lock pin to move inwardly and be struck by the descending spindle nose or (2) permit the tool holder/adapter to work loose from the turret.
It is therefore an object of this invention to provide a mechanism for securely and safely locking a tool holder/adapter in a storage position and to a drive spindle nose.
These and other objects of this invention will become apparent from the following description and appended claims.